In the good old days of Big Ten football — way back in 2015 — the conference season began in Week 5, after teams fed themselves a four-week diet of nonconference opponents of varying strength.

Beginning last year, however, the Big Ten added a ninth conference game, which prompted the league to start its season a week earlier. And this year, a TV-influenced change saw Ohio State and Indiana meet in the season opener.

We don’t have that pure conference-opening weekend anymore, so Saturday’s slate with three conference games — Penn State at Iowa, Michigan at Purdue and Rutgers at Nebraska — will suffice.

With that in mind, here’s a look at key developments through (mostly) nonconference play:

The favorite is …

Penn State, for now, but Michigan, Ohio State and Wisconsin are lurking.

With two shutouts and a decisive win over rival Pitt, Penn State has the look of a Big Ten champ, and the duo of running back Saquon Barkley and quarterback Trace McSorley might be the best in the country.

The Nittany Lions’ front-runner status will be put to test Saturday night at Iowa, where Michigan’s unbeaten season crashed to earth last year and where Penn State suffered the same fate in 2008. “Look at their record in their home stadium against top 10 teams,” Penn State coach James Franklin said. “It’s pretty darn good.”

Should Penn State leave Iowa City unscathed, it still must survive Michigan and at Ohio State on Oct. 21 and 28. Michigan is 3-0 but took a hit when leading receiver Tarik Black suffered a broken foot last week and is out indefinitely. Ohio State’s 31-16 home loss to Oklahoma showed the Buckeyes’ flaws, particularly in the secondary, but the Buckeyes have enough talent to win the East.

Wisconsin has played in four of the six Big Ten title games, and as usual the Badgers have a solid running game, with freshman Jonathan Taylor (438 yards) emerging. The season-ending stretch — vs. Iowa, vs. Michigan, at Minnesota — is the biggest hurdle to the West Division title.

Surprise, surprise

West Lafayette, Ind., and Lincoln, Neb., are home to the biggest surprises, for differing reasons.

Under new coach Jeff Brohm, Purdue no longer is a punching bag. The Boilermakers (2-1) opened with a seven-point loss to Louisville, and their 34-3 win at Missouri boosted confidence. “It does show what you can accomplish if you play extremely hard,” Brohm said.

Picked among the Big Ten West favorites, Nebraska instead is 1-2 with losses to Oregon and Northern Illinois and a narrow win over Arkansas State. On Friday, Nebraska fired athletic director Shawn Eichorst, and many among the Huskers faithful are calling for coach Mike Riley’s job, too.

What about the Gophers?

Minnesota’s 3-0 start under P.J. Fleck has been heavy on substance — strong run game, safe passes, strangulating defense — but light on style. “Is it fascinating or cutting-edge?” Fleck asked. “But it’s what our team can handle.”

Just how much the Gophers can handle will start to become clear next week against a vastly improved Maryland team and the following week at Purdue.